1. Field of the Invention
The present invention relates to a method of manufacturing a liquid jet head which ejects a liquid droplet to perform recording on a recording medium, and to a liquid jet head and a liquid jet apparatus.
2. Description of the Related Art
In recent years, there has been used an ink-jet type liquid jet head which ejects ink droplets on recording paper or the like to record characters or graphics thereon, or ejects a liquid material on a surface of an element substrate to form a functional thin film thereon. In the liquid jet head of this type, ink or a liquid material (hereinafter referred to as liquid) is guided from a liquid tank via a supply tube to a channel, and pressure is applied to the liquid filled in the channel, to thereby eject the liquid from a nozzle communicating to the channel. At the time of liquid ejection, the liquid jet head or a recording medium is moved to record characters or graphics, or to form a functional thin film in a predetermined shape.
As the liquid jet head of this kind, there is known a shear mode liquid jet head. In the shear mode liquid jet head, a large number of grooves arranged in parallel to each other are formed in a top surface of a piezoelectric material substrate subjected to polarization treatment in a direction perpendicular to the top surface, and an electric field is applied in a direction of the thickness of a side wall between adjacent grooves to cause thickness slip deformation of the side wall. In this manner, pressure is applied to the liquid filled in the groove to eject a liquid droplet from the nozzle communicating to the groove. In recent years, along with the demand for higher density in recording dots, pitches of the grooves are becoming narrower, and an electrode pattern is becoming finer.
Japanese Patent Application Laid-open No. 2002-172789 describes a method of manufacturing a liquid jet head, including forming a large number of grooves in the piezoelectric material substrate and forming a conductive film by an electroless plating method. First, two piezoelectric material substrates, which are each subjected to polarization treatment in the direction perpendicular to the substrate surface, are bonded to each other with an adhesive under a state in which their polarization directions are directed to be opposite to each other. Next, the entire upper surface of the piezoelectric material substrate is covered with a liquid resist or a dry film, and the liquid resist or the dry film is cured. Next, a dicing blade is used to form parallel grooves in a plurality of rows, which each have a groove width of 70 μm and a depth of 300 μm. Next, hydrophilic treatment is performed to reform the top surface of the piezoelectric material substrate, and then plating pretreatment is performed so that plating catalyst adheres on the entire surface of the piezoelectric material substrate. Next, a plating film is formed by an electroless plating method. Next, the resist film (or the dry film) as well as the plating film is removed from upper surfaces of drive walls by a lift-off method for removing the resist film (or the dry film).
FIG. 22 is a perspective view of a piezoelectric material substrate 101 obtained after the above-mentioned treatment (FIG. 7 of Japanese Patent Application Laid-open No. 2002-172789). The piezoelectric material substrate 101 includes channel portions 102 formed of a large number of parallel grooves. The channel portions 102 are separated from one another by drive walls 103. In the upper surface of each of the drive walls 103, a plating film 120 is removed by the lift-off method and the piezoelectric material substrate 101 is exposed. Other surfaces are covered with the plating film 120.
Next, a photosensitive electrodeposition resist is caused to adhere to the piezoelectric material substrate 101 to form a resist film 130 on the plating film 120. Next, a region in which the electrode pattern is to be formed is shielded from light by a light shielding mask, and ultraviolet light is applied for exposure. Next, the substrate is immersed in developer to remove the resist film 130 in a region in which the plating film 120 is to be removed, and thus the plating film 120 is exposed. FIGS. 23A to 23C illustrate the surfaces of the piezoelectric material substrate 101 on which the pattern of the resist film 130 is formed by the exposure and development (FIG. 9 of Japanese Patent Application Laid-open No. 2002-172789). FIG. 23A illustrates a front end surface of the piezoelectric material substrate 101. The resist film 130 on the entire front end surface is removed by the exposure and development, and the plating film 120 is exposed at the entire front end surface. FIG. 23B illustrates a rear end surface of the piezoelectric material substrate 101. The plating film 120 on the rear end surface of each of the drive walls 103 is exposed in a vertical direction. FIG. 23C illustrates a bottom surface of the piezoelectric material substrate 101. The plating film 120 is exposed continuously to each plating film 120 exposed on the rear end surface. Next, etching treatment is performed to remove the exposed plating film 120.
FIGS. 24A to 24C illustrate the surfaces of the piezoelectric material substrate 101 after the etching treatment, and correspond to FIGS. 23A to 23C, respectively. The plating film 120 is removed from the front end surface of the piezoelectric material substrate 101 to expose the piezoelectric material substrate 101, and an electrode 104 remains on the side surface of the drive wall 103 (FIG. 24A). On the rear end surface of the piezoelectric material substrate 101, there is formed an electrode pattern 150 which is electrically isolated by portions 140 obtained by removing the plating film 120 (FIG. 24B). On the back surface of the piezoelectric material substrate 101, the electrode pattern 150 is formed, which is electrically connected to the electrode pattern 150 formed on the rear end surface (FIG. 24C). Next, a cover member (not shown) is bonded to the top surface of the piezoelectric material substrate 101 so as to close the respective grooves, and a nozzle plate is adhered to the surface of the piezoelectric material substrate 101 on the front side, from which the plating film 120 is removed. Further, a flexible printed board is bonded to the bottom surface of the piezoelectric material substrate 101 via an anisotropic conductive film, thereby electrically connecting wiring on the flexible printed board and the electrode pattern 150 on the bottom surface to each other.
When the electrode is formed through immersion into the plating liquid, in order to ensure the adhesiveness between the piezoelectric material substrate 101 and the plating film 120, pretreatment is required for the surface of the piezoelectric material substrate 101 before plating treatment is performed. However, the resist film has no resistance with respect to pretreatment liquid, and thus the resist film 130 dissolves and peels off due to the pretreatment liquid. Therefore, as described in Japanese Patent Application Laid-open No. 2002-172789, it is difficult to uniformly remove the plating film 120 from the upper surfaces of the drive walls 103.
In view of this, it is conceivable to deposit the conductive film by a vapor deposition method without using an electroless plating method as described above, and form the electrode pattern by a lift-off method. However, in recent years, the pitches are becoming narrower and the groove width of the channel portion 102 is becoming smaller. A metal vapor cannot easily enter a narrow groove at the time of vapor deposition, and it is required to perform the vapor deposition for a long period of time to form the drive electrode having a necessary thickness on the wall surface. Therefore, a thick metal film is deposited on the upper end surface of the drive wall 103, and thus removal by the lift-off method becomes difficult.
Further, in Japanese Patent Application Laid-open No. 2002-172789, the resist film 130 is formed on the plating film 120, the light shielding mask is placed separately on each of the rear end surface and the bottom surface of the piezoelectric material substrate 101 for exposure and development, and then the plating film 120 is etched to form a pattern. Therefore, the manufacturing process is long, and a large amount of time is required for electrode pattern formation.
Further, another conceivable method is to form a pattern of the plating film 120 by laser processing without using a lift-off method, photolithography, and an etching method. However, in the laser processing, the electrode pattern is required to be processed line by line, which still requires a large amount of time for electrode pattern formation.